Lubricant compositions

ABSTRACT

LUBRICANTS HAVING ADDED THERETO A SMALL AMOUNT OF A MIXTURE OF AN ACYLAMIDO DIARYLAMINE AND A DI(ALKARYL) AMINE HAVE INPROVED OXIDATION STABILITY.

United States Patent Oifice 3,798,166 Patented Mar. 19, 1974 ABSTRACT OFTHE DISCLOSURE Lubricants having added thereto a small amount of amixture of an acylamido diarylamine and a di(alkaryl) amine haveimproved oxidation stability.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to lubricant compositions having improved oxidation stability.More particularly, the invention relates to such compositions comprisingsmall but effective amounts of an additive that has the ability toreduce oxidation of the lubricant.

Description of the prior art Lubricating oils and greases are subject tooxidative deterioration at elevated temperatures or upon prolongedexposure to the elements. The deterioration is evidenced, in manyinstances, by an increase in acidity and in viscosity, and when suchdeterioration is severe enough, it can cause metal parts to corrode.Additionally severe oxidation leads to a loss of lubricating propertiesof the oil, and, in aggrevated cases, to complete breakdown of thelubricated part or of the entire machine. -In combatting oxidation, manyadditives have been tried, but many of them are only marginallyelfective except at high concentrations, especially when the lubricantsare subjected to drastic oxidizing conditions.

;U.S. Pat. 3,377,315 discloses the use of one of the members of theinventive mixture, i.e. an acylamino diphenylamine as a stabilizer fornatural and synthetic polymers and mineral oils. In addition, U.S. Pat.1,907,- 545 teaches the use of m-acetylaminophenyl-beta-naphthylamine toincrease aging resistance of rubber-like products.

SUMMARY OF THE INVENTION The invention provides a lubricant compositioncomprising a major amount of a lubricant and an amount suificient toinhibit oxidation thereof of a mixture of an acylamido diarylamine and adi(alkaryl)amine.

DESCRIPTION OF SPECIFIC EMBODIMENTS The acylamido diarylamines useful inthe practice of the present invention correspond to the formula rl r ANH LA J NH R wherein Ar and Ar are selected from the group consisting ofphenyl, naphthyl, anthryl and phenanthryl and R contains from about 4 toabout 18 carbon atoms and is selected from the group consisting ofalkyl, cycloalkyl, lower alkyl-substituted cycloalkyl and alkenyl. The

0 NHJJJR group may be attached at any of the available positions.

The di(alkaryl)amine utilizable with the above acylamido diaryl aminehas the formula wherein Ar" and Ar' are selected from the groupconsisting of phenyl and naphthyl and R and R" are alkyl of from about 4to about 18 carbon atoms.

When used as antioxidants, the mixtures of this invention are effectivewhen they constitute from about 0.005%

to about 15% by weight of the lubricant base. Preferably,

anes and the like. Especially useful are those synthetic esters whichare becoming more and more popular, particularly in aviation. Theseinclude esters made from polycarboxylic acids and monohydric alcohols,such as those obtained by reacting methanol, ethanol, propanol, butanol,neopentyl alcohol and the like with pimelic acid, azelaic acid, adipicacid and the like, or from polyhydric alcohols and monocarboxylic acids.Of these preferred members are those made from trimethylol alkanes,where alkaneincludes ethane, propane and butane, pentaerythritol, diandtripentaerythritol, or mixtures thereof and an aliphatic monocarboxylicacid containing from 1 to about 20 carbon atoms or a mixture of suchacids. The most preferred are esters from the pentaerythritols andmonocarboxylic acids having from 5 to 9 carbon atoms, or mixtures ofthese acids.

The following examples will serve to specifically illustrate thepractice of the invention. It will be understood that they areillustrative only, and are not intended to limit the scope of theinvention to a narrower range than described hereinabove.

EXAMPLE 1 N- (4-anilinopheny1) pivalamide To a solution of 92 g. ofN-phenyl-p-phenylenediamine in 300 ml. of pyridine there was addedduring nearly 0.75 hour 61 g. of pivaloyl chloride while stirring.During the addition the temperature was maintained at 2530 C. byexternal cooling. The temperature was raised to 45 C. while stirring wascontinued for an additional 1.5 hours. The reaction mixture was pouredinto an excess of ice-water. The organic part was taken up in ether. Theether solution was washed with aqueous caustic solution, then with waterand dried. Solvent was removed and the residue was recrystallized frombenzene to afford the N- (4-anilinophenyl)pivalamide, melting at l28130C.

EXAMPLE 2 N- (2-anilinophenyl) pivalamide This product was prepared bythe method of Example 1 using 46 g. of N-phenyl-o-pehnylenediamine in150 ml.

, of pyridine and 30.5 g. of pivaloyl chloride. Recrystallization fromethanol gave N-(2-anilinophenyl)pivalamide, a crystalline solid, meltingat ll6l18 C.

EXAMPLE 3 N-(4-anilino-1-naphthyl)pivalamide This product was preparedby the method of Example 1 using 10 g. of 4-anilino-l-naphthylamine inml. of pyridine and adding 6 g. of pivaloyl chloride in 50 ml. of1,2-dimethoxyethane. Addition was at 22-28 C. during. 1.25 hours;reaction time was 3.25 hours at 100 C.N-(4-anilino-1-naphthyl)pivalamide was recrystallized 3 from ethanol toaiford a crystalline solid melting at 174 176 C.

EXAMPLE 4 4-(4-anilino-1-naphthy1)lauramide To a mixture of4-anilino-1-naphthylamine and 100. ml. of triethylamine dissolved in 100ml. of dimethoxyethane, 10.5 g. of lauroyl chloride was added duringabout 1 hour at 2226 C. while stirring and cooling with an ice-waterbath. The reaction mixture was then refluxed at 90 C. while stirring foran additional 3.75

hours and then poured into water. The crude N-'('4-"anilino-1-naphthyl)lauramide which precipitated was collected andrecrystallized from ethanol to give a crystalline solid melting at101102 C.

EVALUATION OF PRODUCTS Oxidation test The compounds produced inaccordance with this invention were blended into a synthetic ester oillubricant (made by reacting pentaerythritol with an equimolar mixture ofC and C monocarboxylic acids) and tested in oxidation test in accordancewith the following proce-'. dure.

A sample of the test composition is heated and air at the rate of about5 liters per hour is passed through for a period of about 24 hours.Present in the test sample are specimens of iron, copper, aluminum, andlead. The kinematic viscosity, measured at 100 -F. (percent KV change)and the change in the neutralization number (NN change) are reliableindicators of an additives antioxidant effectiveness. Lead loss isdetermined by weighing the sample prior to the start of the procedureand once again after it is completed. An improvement in either or all ofthese indicates that an additive is elfectively reducing the effects ofoxidation. It should be noted that the metals are typical metals ofengineer machine construction and that they provide some cat;

alysis for the oxidation of organic materials. The results,

are tabulated in the following table.

X VAN 81 is p,p-di'octyl diphenylamine.

It may be seen from the above data that "the combina tion of additivesimproves at least one of the indicators of oxidation. For instance, thecombination of the Example 2 product with VAN 81 gives an unexpecteddecrease in lead loss.

Among the other acylamido 'diarylamines which may be used are thefollowing.

O l]; I ArNH{Ar}NH R Compound Ar Ar R 1 Phen 1 Na hthyl Butyl. 2 dz rOctyl. 3---- do Phenyl Tetradecyl. 4 Naphthyl..... Naphthyl-.-Octadecyl.

Phenyl Anthry1 Cyclohexyl. do .-Phenanthry1 Methylcyclohexyl. 7 doNaphth Butenyl.

rln dn Pentenyl.

Included among the other di(alkaryl)amines which 7 may be used are thefollowing.

Octadeeyl .do -.do Octadecyl.

Either of these can be combined with the acylamido diarylamines above toprovide eifective antioxidant mixtures for lubricants. In other wordsCompound A may be mixed with Compounds l-8 in accordance with thisinvention. So in turn may Compounds 13, C and D be mixed with Compounds1-8.

*Although'the present invention has been described with certain specificembodiments, it is to'be understood that modifications and variationsmay be resorted to without departing from the spirit and scope of thisinvention as those skilled in the art will readily understand. Suchmodifications and variations are considered to be within the purview andscope of the appended claims.

I claim:

1. A lubricant composition comprising a major amount of a lubricant andan antioxidant amount of a mixture of (1) an acylamido diarylamine ofthe formula 0 Ar-NH-Afl-NHii R wherein Ar and A1" are selected from thegroup consisting of phenyl, naphthayl, anthryl and phenanthryl, and Rcontains from 4 to 18 carbon atoms and is selected from the groupconsisting of alkyl, c'ycloalkyl, lower alkylsubstituted cycloalkyl andalkenyl, the

0 Nat group being attached at any of the available positions and (2.) adi(alkaryDamine of the formula wherein Ar" and Ar' are selected from thegroup consisting of phenyl and naphthyl and R and -R" are alkyl of from4 to 18 carbon atoms.

2. The composition of claim 1 comprising from about 0.005% to about 15%by weight thereof of said mixture. 3. The composition of claim 1 whereinthe lubricant is a lubricating oil or grease. i 4. The composition ofclaim 3 wherein the lubricating 4 oil is a synthetic ester lubricatingoil.

5. The composition of claim 1 wherein the diarylamine is N-(4-anilinophenyl)pivalamide and the di(alkaryl) amine is p,p'-dioctyldiphen'ylamine.

6. The composition of claim 1 wherein the diarylamine isN-(2-anilinophenyl)pivalamide and the di(alkaryl) amine is p,p'-dioctyldiphen'ylamine.

7. The composition of claim 1 wherein the diarylamine is N-(4anilino-1-naphthyl) pivalamide and the di( alk-aryl) amine isp,p-dioctyl diphenylamine.

8. The composition of claim 1 wherein the diarylamine isN-(4-anilino-4-naphthyl)lauramide and the di(alkaryl) amine isp,p'-dioctyl diphen'ylamine.

References Cited UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. 3798166 Dated March 19, 97

Inventofls) MI L ID It is certified that error appears in theabove-identified patent "and that said Letters Patent are herebycorrected as shown below:

Col. 3, line L- t-Anilino, etc should be N- L-Anilino, etc.

Col. 3, line 52, "5" should be 5M Col. L, line 31, "naphthayl" should benaphthyl Signed and sealed this 30th day of July 1971 (SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

